1. Field of the Invention
The present invention relates to a puffer-type gas blast circuit breaker for use in electric power system in which a breaker section is incorporated in closed container filled with an insulating gas.
2. Description of the Related Art
The Japanese Utility Model Registration Application No. 01-087840 (Japanese Utility Model Publication No. 03-026943) discloses a puffer-type gas blast circuit breaker capable of preventing an insulating gas heated by arc at the time of breaking from getting into an insulating support through a hollow part of a piston rod.
This puffer-type gas blast circuit breaker disclosed in the Japanese Utility Model Registration Application No. 01-087840 (Japanese Utility Model Publication No. 03-026943) comprises a stationary electrode section 10 and a moving electrode section 20 as shown in FIG. 4A. The stationary electrode section 10 is provided with a stationary side arc contact 13 at the center and a stationary side main contact 12 at the outer circumference. These stationary side arc contact 13 and stationary side main contact 12 are supported by a stationary side electrode support 11. The moving electrode section 20 is provided with a moving side arc contact 21 at the center and a moving side main contact 24 at the outer circumference. The moving electrode section 20 is further provided with an insulating nozzle 23 for blasting an arc generated at the time of breaking with a pressurized gas, and a puffer cylinder 22 that generates a pressurized gas at the time of breaking. The mentioned stationary electrode section 10 and moving electrode section 20 are disposed facing each other so as to come in contact with and go separating from each other, and a breaker section surrounded by an insulating cylinder 4 is formed. This breaker section is mounted on a stationary member 26 supported on an insulating support 27.
In the moving electrode section 20, a hollow piston rod 31, an insulating rod 32, and an operating rod 33 are connected in order. These connected rods run through a body portion 26a of the stationary member 26, and further connected to an operating device 34. In the piston rod 31, the moving side arc contact 21 is connected to a tip of one end of the piston rod 31, and the piston rod 31 is formed to be hollow with its other end closed. Furthermore, the piston rod 31 is provided with a heated gas jet port 31a at the other end side for jetting out a heated gas laterally. The insulating rod 32 is capable of insulating from the operating device 34 and transferring an operating force. A gas flow blocking member 35 is mounted on the connection part between the piston rod 31 and the insulating rod 32 so that the insulating support 27 may be prevented from the insulating gas heated at the time of breaking that might get in from the inner circumference of the piston rod 31.
When this known puffer type gas blast circuit breaker constructed as mentioned above begins the contact opening operation, the stationary side main contact 12 and the moving side main contact 24 are opened and separated from each other, and then the stationary side arc contact 13 and the moving side arc contact 21 are opened and separated from each other, thereby arc being generated. Then, the arc is blasted with an insulating gas pressurized at a puffer chamber 22a of the puffer cylinder 22, whereby the insulating gas is heated by the arc and jetted out of the insulating nozzle 23 to the stationary side electrode support 11. At the same time, the insulating gas jets out of the hollow part of the piston rod 31 into the body portion 26a of the stationary member 26 through the heated gas jet port 31a to be cooled by being mixed with the insulating gas of normal temperature remaining in the body portion 26a, then is discharged from a gas discharge port 26b of the body portion 26a of the stationary member 26 into the closed container 1.
The manner of flow of the insulating gas discharged out of the piston rod 31 in the opening and separating process of the stationary electrode section 10 and moving electrode section 20 at the time of breaking in the conventional puffer-type gas blast circuit breaker of above construction is discussing more specifically with reference to FIGS. 4A and 4B.
FIG. 4A shows a closed state of the stationary electrode section 10 and moving electrode section 20, FIG. 4B shows an intermediate stage of the separating process, and FIG. 4C shows an opened state of the stationary electrode section 10 and moving electrode section 20.
In the closed state of the stationary electrode section 10 and moving electrode section 20 shown in FIG. 4A, the gas flow blocking member 35 is located at a position on the breaking section side of the body portion 26a of the stationary member 26. In the state shown in FIG. 4B, the gas flow blocking member 35 is located at a position of the gas discharge port 26b of the body portion 26a of the stationary member 26. In the opened state shown in FIG. 4C, the gas flow blocking member 35 is located on the insulating support side of the body portion 26a of the stationary member 26.
As mentioned above, in the conventional puffer-type gas blast circuit breaker, the gas flow blocking member 35 is located at the position of the gas discharge port 26b of the body portion 26a of the stationary member 26 in the separating stage as shown in FIG. 4B. Accordingly, at the time of breaking, the insulating gas jetting out of the piston rod 31 through the gas discharge port 31a runs around the outer circumference of the gas flow blocking member 35, coming into the inner circumference on the insulating support side (lower side in the drawing) of the body portion 26a of the stationary member, then gets into the inner circumference of the insulating support 27. When completing the separating operation, as shown in FIG. 4C, the gas flow blocking member 35 is located on the insulating support side of the body portion 26a of the stationary member 26, and the heated insulating gas is now blocked from further getting into the inner circumference of the insulating support 27.
FIG. 5 is a cross-sectional view of the stationary member of FIG. 4 locating at the position of the gas discharge port at the time of completing the separating operation. As shown in the drawing, the heated insulating gas discharged from the heated gas discharge port 31a of the piston rod 31 goes around circumferentially within the body portion 26a of the stationary member 26, and is mixed with the insulating gas of normal temperature in the body portion 26a. As a result, the insulating gas of lowered temperature is discharged from the gas discharge port 26b into the closed container 1, whereby insulation resistance of the insulating support 27 and the closed container 1 can be kept.
In the puffer-type gas blast circuit breaker of above construction disclosed in the Japanese Utility Model Registration Application No. 01-087840 (Japanese Utility Model Publication No. 03-026943), it is to be noted that, during the breaking operation shown in FIG. 4B, the insulating gas getting into the stationary member 26 from the inner circumference of the piston rod 31 goes around the outer circumference of the gas flow blocking member 35, and gets into the inner circumference of the insulating support 27. It is certain that the time, during which the gas flow blocking member 35 is located at the position of the gas discharge port 26b of the body portion 26a of the stationary member 26, is short, but amount of the gas heated at the time of breaking is considerably large. As a result, a problem incidental to the conventional puffer-type gas blast circuit breaker exists in that a large amount of heated gas gets into the insulating support 27, thereby reducing density of the gas of normal temperature in the insulating support 27. Consequently, insulation resistance of the inner surface of the insulating support 27 and the creepage surface of the insulating rod 32 located inside of the insulating support is lowered eventually resulting in improved insulating reliability.